On August 25, 1995, a Boeing 737-3B7 (registration N373US) operated by Usair, Inc. was involved in an aviation accident near Fort Lauderdale, FL. Investigators recorded the probable cause as: Low electrical resistance in the 'B' autopilot aileron actuator, which caused an uncommanded roll during descent for landing while the system was engaged. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 3 related events involving the same aircraft type or operator are linked below.
An aircraft experienced an uncommanded roll to the right during descent for landing while the 'B' autopilot system was engaged, leading to a post-incident examination of the aileron actuator.
What happened
During the descent phase for landing, the flight encountered an uncommanded roll to the right. At the time this event occurred, the 'B' autopilot system was engaged. The sudden movement required immediate attention from the crew as they managed the aircraft's attitude and trajectory.
The investigation
Following the incident, a thorough examination of the aircraft systems was conducted. Post-incident analysis revealed that the 'B' autopilot aileron actuator exhibited low electrical resistance. This finding prompted further testing by Boeing Commercial Airplane Company to understand the implications of this anomaly.
Findings
Tests conducted by Boeing Commercial Airplane Company demonstrated that low electrical resistance within the autopilot aileron actuator is directly linked to uncommanded roll occurrences. This mechanical issue likely contributed to the unexpected aircraft movement during the critical descent phase.
Probable cause
Low electrical resistance in the 'B' autopilot aileron actuator, which caused an uncommanded roll during descent for landing while the system was engaged.
What happened in the 25 Aug 1995 Boeing 737-3B7 accident near Fort Lauderdale, FL?
An aircraft experienced an uncommanded roll to the right during descent for landing while the 'B' autopilot system was engaged, leading to a post-incident examination of the aileron actuator.
What aircraft was involved and where did it happen?
The accident on 25 Aug 1995 involved a Boeing 737-3B7, registration N373US, operated by Usair, Inc., at Fort Lauderdale, FL.
What was the probable cause of the accident?
Low electrical resistance in the 'B' autopilot aileron actuator, which caused an uncommanded roll during descent for landing while the system was engaged.
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